Heart's Sound
by ThObliviate
Summary: Castle decides to make a surprise for Beckett, but what he did not expect was that he would be surprised. Just a fluffy Caskett fanfic. It takes place at some point in season 6.


**I do not own Castle or its characters.**

**English is not my first language. If you find something wrong, please tell me.**

**Just fluffy. Enjoy.**

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It had been a tough week. The team took days to solve a case that seemed to have no solution. Beckett spent much of the past week in front of the murder board, with Castle always by her side, trying to find something that would connect one of the suspects to the crime scene. Every person of interest seemed to have a pretty soft alibi.

Now, after five tortuous days, they finally managed to overthrow the alibi of the victim's boss who said he was at home with his wife. The motive for the crime was that the girl had committed an error in a spreadsheet, which caused the company to suffer a great harm. They managed to arrest the man who, in a fit of rage, killed his employee with a knife.

What really struck an emotional chord Beckett and her team, was the realization that the girl was pregnant when she was killed. The error committed by her was derived from a bad health day when she was throwing up every hour, making it difficult to concentrate on her work.

Because of everything she had been through during this case, Beckett wanted nothing more than to go to Rick's apartment and relax with a glass of wine and her fiance. However, Castle needed to spend the night locked on his office at the loft alone. He had to finish a chapter he should deliver the next day. He'd told her the night before, but the craving for companionship and comfort made her forget this little detail.

"So, I'll meet you at your place for a glass of wine?" Kate asked as she watched Castle get his coat and get ready to say goodbye, leaving her with the paperwork.

"I would love to, but I need to finish that chapter," said Castle looking disappointed, "See you tomorrow?" he added, hoping to cheer her up.

"See you tomorrow," agreed Beckett, feeling terrible for having to spend the night alone.

Castle kissed her temple and headed to the elevator, waving before the doors closed completely. Beckett sat in her chair and began to organize the paperwork regarding the arrest of the man. However, after ten minutes of a work that didn't progress, she decided to go home and finish the job the next day.

As for Castle, the truth was that he was not even slightly concerned about the apparent delay in the submission of his next chapter. The case had also shaken him and he just wanted to spend the night with Kate. He planned to make a surprise, appearing at the door of her apartment with a bottle of her favorite wine. He was hoping that it would cheer her up a little bit. It and his companionship, of course. After murder cases like this one, the comfort one could offer the other was the best medicine.

Then, Rick went home, took off the clothes from work, switched them to one of his plaid shirts and jeans and grabbed a bottle of wine from the stock kept at the loft for when Kate would spend the night, what was happening almost every day now. He wrote a note to Alexis, telling her where he would be and only after that he left and took a cab to Kate's apartment. As soon as he entered the cab, Rick straightened his hair in a manner typical of Castle, looking at his reflection in the window.

Castle arrived at the Kate's building and went to her apartment. As he left the elevator and stepped on her floor, Rick heard a song he had never heard before being sung by a slightly familiar angelic voice. He paid attention to the words and discovered it was telling a beautiful love story. Curious as always, he followed the sound without hesitation and got a little surprised when it took him to Beckett's apartment. Normally, when he resolved to make her a surprise, her apartment was silent and Kate was lying comfortably on the couch, reading a book.

Never in six years had he heard a song playing after a hard day's work at that place. One time, on the beginning of their relationship, Castle asked her why she didn't listen to a good music after work, Beckett simply answered: "It's not like I do not like music. But I need to hear all kind of noise all day at work. When I get home I just want to relax, have a glass of wine and read a good book."

After thinking about all this, Castle got even more curious and felt an incredible need to find out what caused this sudden change in Beckett. Once he recovered from the shock, he took the keys she had given him as soon as they got engaged and quietly opened the door, still intending to keep the idea of a surprise that had initially brought him there.

However, what Rick did not expect was that he would be surprised. When he entered the apartment he saw something that would be etched in his mind forever. Kate, his Kate, was sitting on the edge if her sofa extremely focused on what she was doing.

Not that it was abnormal. Kate always stood 100% focused when doing something. That did not surprise him. What really stunned him was the fact that the music he had heard previously was being sung and played by Beckett. She had a guitar on her lap and carefully strummed notes of that wonderful music. She was singing with passion, observing the movement of her hands on the neck of the guitar. Because of this, she did not notice the sudden entrance of Castle and remained singing. Rick stood at the entrance of the apartment and watched his fiancée finishing the song. He now realized that it was telling their history. He had nothing but love and devotion to the woman in front of him in his eyes.

When Kate finished playing and the apartment was silent, she looked up and saw the writer standing in the same place he was since he closed the door. He was still watching her as if he had not realized the music had ended. Beckett's mouth opened in the shape of a perfect "O". She wasn't expecting any visitors. Much less his visit after what he had told her at the precinct. As long as she would stay home alone, she decided to do something she loved but didn't do in a long time: play the guitar. None of her friends, not even Lanie, knew about this hidden talent.

Oftentimes when she was alone at home Kate composed her own songs and sang them to the accompaniment of her guitar, a gift from her mother for her 16th birthday.

"I didn't know you could play the guitar," Castle interrupted her thoughts.

"Uh…I…I can play a little bit…" Kate said shyly, looking down at her feet and nervously biting her lip.

"You are extraordinary," answered Rick, approaching her and putting a lock of hair gently behind her ear before kissing her deeply, showing all the love he felt. "Even after years you still manage to surprise me," he added when they stopped the kiss.

"Well, I think you were right when you said I was a mystery you were never going to solve. But you're getting pretty close, I must say," grinned Kate.

"Why didn't you tell me you could sing?"

"You already knew I could sing. Technically. Do you remember when you bought the "Old Hunt"? We sang a song on the way there."

"You know it isn't what I meant. Why didn't you tell me you could sing and play the guitar so well?" He asked again.

"I don't know," Kate bit her lip once more, "I've never shared this talent with anyone. Actually, besides my dad, you are the only one who knows."

He smiled at the sudden revelation. "When did you learn how to sing and play?"

"What? Are you interrogating me now?" laughed Beckett.

"It's ok if you don't want to tell me… It was an ex-boyfriend who taught you, wasn't it?"

"Rick, none of my ex-boyfriends knew that. My mom taught me when I was 16. We used to sit together when I was a little girl. My mother played the guitar and sang, my father drummed his fingers on the table and I danced around the house. When I grew up, I began to follow my mother in the song, and when I was old enough she taught me how to play," her eyes filled with tears due to good memories the story brought. Castle put an arm around her shoulders and pulled her close to him.

"I'm glad to know this about you," said Rick, still surprised, even after more than one year, at how easy she shared memories with him now, "But I'm sorry for making you cry," he added while he lovingly stroked her arm.

"It's a good memory, Rick. I'm happy for sharing it with you," Kate snuggled further into Rick's chest.

They remained silently for a few minutes, lost in their own thoughts and enjoying being together after such a difficult week. Suddenly, Castle remembered that he still had some question to ask her. "Was it you who wrote that song?" he suddenly asked before he could stop himself.

"Yeah, you like it?" Beckett pulled away from Castle just enough so she could look into his eyes, "I know it's not a big thing, but I wrote it with my heart and I always enjoyed composing and…"

"I loved it!" interrupted Rick, "When did you write it?"

"Hum… Last year, when I left you so you could finish writing your book."

"Does that mean that whenever you let me alone so I can write you come home and compose your own songs and play the guitar?"

"Not always. Only when I feel lonely. Playing and singing, as well as watching "Temptation Lane", makes me feel safe."

"I'm sorry for letting you alone," Rick hugged her again and kissed her hair, "The truth is that not even for a second I intended to spend the night writing. I was planning on make you a surprise," he added, grabbing the bottle of wine that was forgotten and showing her.

"Oh! So you brought my favorite, uh?" said Beckett unable to hide the smirk that appeared on her lips.

"Hey! My intentions are nothing but pure," Castle tried to defend himself, but his gaze, which was fixed in Kate's mouth, contradicted him.

"Then you came just to visit me, right? Don't you intend to spend the night here?" Beckett slowly approached Castle, teasing him. But, before he could kiss her, she pulled away quickly, taking the bottle of wine with her so she could serve a glass for both of them. A smile of amusement appeared on Kate's face as she saw the look of confusion and surprise on the writer's face.

"Uh, what did you say?" Castle asked, confused, almost a minute later when he got out of the trance caused by the sudden teasing.

"You are so easy, aren't you?" Beckett laughed openly.

"That's not funny," said Rick, feigning annoyance. He rose from the couch and followed Kate to the kitchen.

"You are pretty much mistaken. This is hilarious!" but Kate wasn't laughing anymore. She drank her wine, smacking and slowly biting her lips after tasting the familiar flavor. She was once again teasing him.

"If you keep doing that I'll be forced to kiss you."

"Then shut up and kiss me."

Castle didn't need to be told twice. He advanced to Kate, ran his hand around her waist and kissed her passionately. As soon as she felt the contact of his lips on hers, Beckett laced her fingers on Rick's hair and deepened the kiss.

"I want to listen to you singing again, Kate. You're amazing," Rick said as they pulled away due to lack of air. He gently stroked her cheek, looking into her eyes and showing all the love he felt for her with that single look.

"Always," assured Kate, returning the look and expressing the feeling of as much love for this amazing man as he felt for her, "Always, Rick," she repeated before rising on her tiptoe to kiss him again.

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**I hope you like it. Let me know what you think**


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